Choosing a satellite antenna: fixed, flyaway, drive-away, COTM or maritime

Antenna selection usually starts with the wrong question. People ask how large a reflector they need, when the answer is almost always determined first by how the site moves, how quickly it must be on air, and who will point it.

Start with mobility, not gain

Five categories cover nearly every requirement, and they are separated by motion rather than by size.

• Fixed earth station. The site does not move. Reflectors from roughly 1.2 m to 16 m, permanently mounted, aligned once by a commissioning team. Highest gain per unit cost, and the only option for a teleport or hub.
• Flyaway. The site moves, but the antenna is stationary while in use. Packs into transit cases, assembles by hand in minutes, deploys manually or automatically. Chosen when the equipment must travel as baggage or freight.
• Drive-away. The antenna travels stowed on a vehicle roof and deploys automatically on arrival. No assembly, no tools. Chosen when the crew is small and the time between arriving and being on air matters.
• Communication on the move (COTM). The antenna tracks the satellite while the vehicle is moving. Low profile, lightweight, continuously stabilised. Chosen when stopping to deploy is not acceptable.
• Maritime. A stabilised antenna inside a radome that holds the satellite through roll, pitch and yaw, indefinitely. Chosen for any vessel.

What each choice costs you

Moving up that list buys convenience and pays for it in aperture. A COTM antenna that fits a vehicle roof has far less gain than a 2.4 m fixed reflector, which means a smaller link budget, a lower data rate for the same power, or more satellite capacity to achieve the same rate. That is not a flaw; it is the trade you are making. The mistake is discovering it after the network is designed.

Deployment time is the other axis. A manual flyaway can be on air in minutes by a trained pair of hands. A drive-away is on air in minutes by one person pressing a button. A fixed station is on air in weeks and then stays there.

The interoperability question people forget

An automatic antenna has a controller, and that controller has to talk to the modem to know when it has found the right satellite. If the two were not designed together, they may share no interface or protocol at all. This is the single most common cause of a system that works on paper and not on site.

It is solvable. A Protocol & Port Converter sits between the controller and the modem and translates, which is why we supply one alongside COTM systems as a matter of routine rather than as an afterthought.

A short checklist

• Does the site move, and does it transmit while moving?
• How long between arriving and needing to be on air?
• Who points it: a commissioning engineer, a trained operator, or anyone?
• Which band, and is the satellite operator’s type approval already in place?
• What is the worst weather the site will operate in?
• Does the antenna controller share an interface with the chosen modem?
• Who performs installation, commissioning tests and training?

Our antenna range covers all five categories, with system integration, installation, commissioning, training and support.